hot take: if you’re making microcontroller boards or single-board computers and you don’t want to do the software so you leave that up to the community that you hope shows up to both purchase the hardware and implement the software for you, the very least you could do is make UART and reflashing an inline operation with one of the ports on the device without any dongles or wack-ass flashing programs on the host side - just send bits in the interface, they get written to the flash. like, c’mon. give us that much.